package com.b;

import java.util.Scanner;

/**
 * @author LW
 * @2020/10/9 10:26
 */
public class task2 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.println("输入:");
        int n = scanner.nextInt();
        int num =1;
        for (int i = 0; i < n; i++) {
            num = num+ (21+i);
        }

        System.out.println(num);
    }
}
